Beginning around A.D. 600, Ancestral Puebloans built Colorado's first permanent towns in the canyon country south of here. Hundreds of settlements spread across the desert, with an overall population possibly greater than the region holds today. Larger communities such as Yellow Jacket and Lowry Pueblos housed several hundred people each in great houseblocks with many rooms, while residents stored food in stone granaries, built small dams and reservoirs for water storage, and raised corn, beans, and squash in terraced plots. After prospering for hundreds of years, these peoples left their homes for reasons that included climatic changes, increased warfare, and social upheavals, and by 1300 these communities stood empty. Anglo-Ute relations in Colorado reached a low point on June 19, 1885, when a group of cowboys ambushed a peaceful Ute camp on Beaver Creek miles southeast of here. Since a bloody 1879 conflict at the Ute agency in northeastern Colorado, racial tensions had remained high, and the slogan "The Utes must go" had become a cry among white settlers. The attackers at Beaver Creek took that slogan literally, killing at least six and perhaps as many as ten people, including women and children. The Utes retaliated by killing a white rancher, and further violence followed, though mediation by Indian agents prevented more. The Utes had official permission to hunt in this area to supplement their meager government rations, yet the cowboys involved in the Beaver Creek Massacre had vowed to kill any Indian found off the reservation.